Save our storage (or why your food storage container turns orange)

01 August, 2016

It’s a common enough problem – you put your leftover takeaway into a plastic food storage container and leave it in the fridge for tomorrow. In the morning there are orange stains on your container, which do not come off even with intensive cleaning. The issue is that coloured stains from oily foods become embedded in the plastic and can’t be cleaned off, even in the dishwasher.

In this area perhaps things really were better in the old days, with older plastic containers being much more resistant to staining and offering a clear, tough, durable, and heat resistant alternative to glass. The problem was that these containers were made from polycarbonate and bisphenol A (BPA), a chemical used in the manufacture of polycarbonate which has the potential to interact with human hormone systems as an 'endocrine disruptor'. Although studies have shown that the levels of BPA found in food from food contact materials are not a concern to health[1], following consumer reaction most manufacturers chose to remove polycarbonate from their products to allow labelling as “BPA-free”. In the US the Food & Drug Administration (FDA) then ended its authorisation of the use of BPA in baby bottles and sippy cups, based on manufacturers abandoning the use of polycarbonate in these products.

This created a significant headache, as alternative food packaging materials proved to be more expensive, to have lower performance, or were themselves suspected as having human endocrine activity (which can occur at extremely low concentrations). As well as staining by coloured foods, another drawback with polycarbonate alternatives is the tendency for the initially clear plastic to develop a white/hazy appearance. This tends to happen in the microwave or dishwasher, particularly in commercial kitchens where high temperatures and pressures are used for cleaning.

Many manufacturers now use polyester co-polymers or clarified polypropylene for food containers instead of polycarbonate, but these can suffer from whitening/hazing after a relatively short period of use. Alternative materials have been tried, but it has proved very hard to find something which meets the many performance requirements at an acceptable cost, particularly for coloured, oily or acidic foods.

Despite extensive research on alternative materials, a plastic for transparent food containers which can be shown not to have endocrine activity and works well for all food types currently seems unrealistic. This is particularly true when the environmental impact of producing and discarding large amounts of packaging materials for the global food system is taken into account.

It seems clear then that compromises will need to be made. Whilst we wait for a “safe polycarbonate” material to emerge which doesn’t turn orange when storing your vindaloo, other common problems with plastic food storage containers might prove to be more tractable. One of the most annoying is this – you open your cupboard to find a wide selection of containers and lids, but it takes you half an hour to find a lid which fits. Fortunately a simple solution to this problem is available, although it doesn’t do much for the environment: throw them all out and purchase a replacement set – all the same size.